Throughout this application, the term xe2x80x9cdump truckxe2x80x9d is used. This term is to be interpreted broadly and incorporates both dump trucks and dump trailers.
This invention relates to an alarm system for alerting an operator of a dump truck, when the tailgate has been left unsecured. Unlike other types of automobiles such as pickups, dump trucks have tailgates that pivot about an axis located at the top of the tailgate. When an operator desires to dump a load from the bed of his truck, he must raise the front of the bed. As the front of the bed is raised, the load slides rearward and pushes against the tailgate. The weight of the load causes the bottom of the tailgate to be pushed outward and the load then slides from the bed. Most modern dump trucks are equipped with a safety device that must be actuated by the operator of the dump truck to secure the tailgate. In many dump trucks the operator must release the safety device prior to raising the bed of the truck to dump a load.
Dump trucks are used for a variety of hauling tasks in today""s society. Roadway and building construction sites require vast amounts of fill materials such as sand, gravel or stone. These fill materials are typically hauled in the beds of dump trucks. Additionally, large chunks of rubble from building demolition sites are hauled to land fills in dump trucks. Dump truck loads can shift in the bed during transport and be inadvertently deposited on a roadway surface if the tailgate is not safely latched. Other roadway hazards may be created when debris from an unsecured dump truck falls onto a roadway. For example, gravel from the dump bed of a dump truck, having an unsecured tailgate, may fall onto a road surface and damage an automobile following the vehicle. Gravel falling from dump truck beds typically damages automobiles following the dump truck by breaking headlights and windshields or damaging radiators. Moreover, an operator of a vehicle may be startled if his windshield is suddenly shattered and wreck the automobile.
Most modern dump trucks are equipped with a latch that secures the tailgate and prevents it from inadvertently opening. However, the latch cannot prevent the tailgate from opening if the operator has not properly latched it. Thus, a portion of the load may fall out of the bed and onto the roadway surface thereby creating a roadway hazard. Individuals in automobiles following the dump truck may be hit by a portion of the load that has fallen from the bed of the truck as mentioned above. Alternatively, it may become necessary for the individuals to deviate from their intended course of travel and thereby cause an accident.
U.S. Pat. No. 6,137,419 to Lennox et al. discloses a pickup truck tailgate monitor. In Lennox, a tailgate monitor in an operator""s compartment of a pickup warns the operator if the tailgate is open. A tailgate for a pickup tends to swing to an open position when the tailgate is not secured. Thus, Lennox uses a sensor mounted on the bed to indicate when the tailgate is open. However, the Lennox device cannot be properly used on a dump truck since the tailgate of a dump truck tends to be closed except when the bed is raised.
U.S. Pat. No. 3,789,357 to Fritz, Jr. discloses a safety apparatus for dump trucks. In Fritz, Jr., a safety circuit automatically shuts off the engine of the dump truck when the bed is raised while the tailgate is closed. Another circuit provides a lamp that indicates when the tailgate is opened. However, Fritz, Jr. requires that the bed be raised in order for the tailgate to open. Thus, a load may be deposited in the bed of a dump truck equipped with the Fritz, Jr. device and the lamp may not be lit until a portion of the load has been inadvertently dumped onto a roadway surface.
Neither of these devices can prevent the existence of a dangerous condition such as when the tailgate is in an unsecured closed position. If a dump truck is equipped with either the Lennox or the Fritz, Jr. device, the tailgate may be closed but not secure. Thus, neither Lennox nor Fritz, Jr. contemplates the problem to be solved by the present invention.
The present invention includes a retro-fit kit that may be installed on existing dump trucks to alert an operator of the existence of a dangerous condition. Typically, trucks with dump beds are equipped with braking systems that operate by utilizing air pressure. An air source such as a compressor generates an air pressure that is stored in a bladder or air tank. The air pressure acts in essentially the same manner as fluid in a passenger car""s brake system. As the operator of the dump truck depresses the brake pedal, the air pressure causes the brake shoes to contact with rotating parts of the wheels (rotor).
Since air pressure is a necessary component for actuating the brake system of the dump truck, it must be constantly monitored. Many dump trucks are equipped with an audible alarm that emits a sound when the air pressure in the brake system falls below a set threshold. If the air pressure falls below a second threshold or becomes nil, the brake system of the dump truck will xe2x80x9clock up.xe2x80x9d Thus, the dump truck will not move when the air pressure falls below the second threshold. When the xe2x80x9clow airxe2x80x9d pressure alarm sounds, the dump truck operator must identify the source of the problem or else risk the possibility of losing control of the dump truck.
Many modern dump trucks are equipped with a safety mechanism comprising a safety catch that secures the tailgate on a dump truck. Typically, the safety catch is actuated with pneumatic piston that operates by air pressure. The air pressure may be either positive or negative depending upon the configuration of the system. Likewise, hydraulic systems may be used to actuate the safety catch. For ease of understanding, the positive air pressure is only discussed herein.
The pneumatic piston comprises an air chamber and a piston arm. As air is forced into one end of the air chamber, the piston arm is extended from the piston. If air is forced into an opposite end of the air chamber, the piston arm is retracted into the piston. A linkage is connected to the piston arm for transferring the movement of the piston arm to cause the safety catch to be engaged and disengaged. Using this system, an operator of a dump truck can disengage the safety catch and raise the dump bed to dump a load without leaving the cab of the dump truck.
In a typical arrangement, the piston receives air from either of two air supply hoses. The first air supply hose is connected to the piston on an end opposite the second air supply hose. When an air source supplies a positive air pressure through the first hose, the piston arm is extended from the piston. This causes the safety catch to be released. When the air source supplies a positive air pressure through the second hose, the piston arm is retracted into the piston. If the dump bed is down the tailgate is closed and the safety catch will be activated as the piston arm is retracted into the piston.
It should be noted that the pneumatic piston might be substituted for a hydraulic one that operates similar to the pneumatic piston explained above. Alternatively, the pneumatic piston may be biased in one direction of operation, i.e. extended or retracted, and operated by an air pressure in the opposite direction.
In one embodiment of the invention, the xe2x80x9clow airxe2x80x9d warning indicator is used to alert the dump truck operator that the tailgate is not secured.
In another embodiment, an electrical circuit is provided that alerts the dump truck operator of the dangerous condition. In this embodiment, a lamp or buzzer is located in the operator""s cab of the truck. A switch is located near the piston arm and is connected on one side (contact) to the lamp or buzzer and on the other side (contact) to a voltage source. The switch is connected via conductors such as stranded wire that may be wrapped around or ran through the frame of the truck. The voltage source may be either an independent voltage source or a source supplied from the truck""s electrical system.
It is an object of the invention to provide an alarm that alerts an operator of a dump truck when the tailgate is left unsecured.
It is another object of the invention to provide a method for modifying the existing xe2x80x9clow airxe2x80x9d alarm in a dump truck to alert an operator when the tailgate has been left unsecured.
It is a further object of the invention to provide an electrically operated alarm for alerting the operator when the tailgate is unsecured.